Stabilization of alkyl vinyl pyridines using tertiary butyl catechol and subsequent copolymerization of the alkyl vinyl pyridines with acrylonitrile or acrylate derivatives



STABILIZATION F ALKYL VINYL PYRIDINES USING TERTIARY BUTYL CATECHOL AND SUB- SEQUENT COPOLYMERIZATION OF THE ALKYL VINYL PYRIDINES WITH ACRYLONITRILE OR ACRYLATE DERIVATIVES Richard M. Roeder, Camden, S.C., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Dec. 31, 1963, Ser. No. 334,937

7 Claims. (Cl. 260-805) This invention is concerned with the stabilization of alkyl vinyl pyridines to prevent polymerization and discoloratiom It is further concerned with spinning fibers of good whiteness from a copolymer of acrylonitrile and an alkyl vinyl pyridine.

Alkyl vinyl pyridines are useful co-monomers in acrylonitrile fibers because they impart acid dyeability to the fibers. However, certain problems arise inthe use of alkyl vinyl pyridines. One problem is that alkyl vinyl pyridines will polymerize on standing even at room temperature. Another is discoloration of the alkyl vinyl pyridines, with or without polymerization. And this discoloration is carried over to the acrylonitrile fibers. Furthermore, even clear but uninhibited alkyl vinyl pyridines may cause discoloration of fibers spun from a copolymer .of acrylonitrile and alkyl vinyl pyridines.

Tertiary-butyl catechol (1,2-dihydroxy-4-tertiary-butyl benzene) has been used to stabilize alkyl vinyl pyridines against polymerization. However, tertiary-butyl catechol when used alone has the serious disadvantage of causing, or at least allowing, serious color development.

It is therefore an object of the present invention to inhibit polymerization of alkyl vinyl pyridines during storage.

It is a further object to inhibit discoloration of alkyl vinyl pyridines.

It is still a further object to inhibit discoloration of fibers spun from a copolymer of acrylonitrile and alkyl vinyl pyridines.

It is still a further object to accomplish these results by means which will not itself become a source of discoloration, either in the alkyl vinyl pyridine, or in fibers spun from a copolymer of acrylonitrile and an alkyl vinyl pyridine.

These and other objects will become apparent in the course of the following specification and claims.

These objects are accomplished in the present invention by incorporating into alkyl vinyl pyridines a minor amount of a composition-which comprises a mixture of (A) an alkyl polyhydr-oxy aromatic compound, and (B) at least one member selected from the class consisting of: (1) acrylonitrile, (2) an acrylate, (3) a methacrylate, and (4) a mixture of vinyl acetate and acrylonitrile.

By alkyl vinyl pyridine is meant a compound wherein the vinyl group is attached to one of the ring carbon atoms, and the alkyl group, of less than five carbon atoms, is attached to one of the other four ring carbon atoms. The preferred alkyl vinyl pyridine is 2-methy1 5-vinyl pyridine (hereinafter referred to as MVP).

MVP as shipped usually contains from 1000 to 1500 parts per million (p.p.m.) or 0.1 to 0.15% by weight of tertiary-butyl catechol (hereinafter referred to as TBC). The product is dark colored and unfit for use as a fiber co-monomer without purification. Before use, it must be purified by distillation, either under vacuum or by steam.

Distillation of the MVP not only removes the color but also the TBC. Since alkyl vinyl pyridines polymerize at room temperature if not inhibited, it is necessary to either add inhibitor or keep the MVP refrigerated until used.

.For convenience and safety an inhibitor is preferred.

United States Patent 0 "Ice Furthermore, an inhibitor is necessary for the production of color-free polymer. A polymer of unsatisfactory color will be obtained from uninhibited or poorly inhibited MVP regardless of its color. Therefore, the color of the. MVP is not necessarily an indication of the color of the polymer that will be obtained. A slightly discolored MVP may, if it contains the proper inhibitors, give a polymer of satisfactory color, and a water-white MVP may yield a polymer with too much color if not properly inhibited.

It has now been discovered that acrylonitrile (AN) monomer itself is an inhibitor for MVP. Since the ultimate use of MVP in this invention is for copolymerizing with AN, it is advantageous that AN is also an inhibitor. AN is also copolymerized with alkyl acrylates; and, the further discovery has been made that small amounts of alkyl acrylate monomer, along with the AN, give a superior inhibitor. A small amount of TBC of the order of 0.01% is necessary to further improve the color stability of the MVP and of the copolymer obtained with it. Thus a ratio of AN/methyl acrylate of 94/6 and 0.01% TBC gives very good stabilization and will in no way interfere with polymerization to yield copolymers. Such copolymers have excellent color and yield fibers that will dye readily to clear shades with acid dyes.

Tests of various inhibitors were made, and the results shown in Table II below. Part A of Table II gives the results of inhibitors tested by vacuum distilling the MVP, then adding the inhibitor and storing at 10 C. under nitrogen. The same conditions were employed in part B except that the inhibited MVP was stored under air. Part C shows the results of inhibitors tested by steam distilling the MVP, then adding the inhibitor, and storing at 15 C. under air. Included in Table II are control examples for each testing procedure employed. At time intervals as shown in Tables I and II, the color of the MVP was measured with a Fischer Electrophotometer AC Model at 425 mu. At the same time, the vacuum distilled MVP was tested for the presence of polymer by adding ten parts of hexane to one part of MVP. The development of turbidity will give a rough indication of the amount of polymer present. Steam distilled MVP contains water and this test will not apply.

Table I indicates the significance of the symbols in Table II.

, Table I AN: acrylonitrile MA=methyl acrylate VA=vinyl acetate ANMA-=blend of 94 parts AN and 6 parts MA ANVA=blend of 94 parts AN and 6 parts VA TBC: 1,2-dihydroxy-4-tertiary-butyl benzene MEHQ=methy1 ether of hydroquinone MVP: Z-methyl-S-vinyl pyridine Table ll.Stabilizati0n 'of methyl vinyl pyridine A.VACUUM DISTILLED, STORED UNDER AIR Color Values- Example 4 Days 14 Days 35 to 45 Days 1. 1.0% AN- 11 16 1 38 2. 15.0% 9 8 1 21 3. 0.94% AN+0.06% MA 11 23 1 51 4. 9.4% AN+0.6% MA 8 13 26 5. 4.7% AN+0.3% MA+0.01% TBC 9 10 26 6. 4.7% AN+0.3% MA+0.10% TBC 9 9 14 7. 5.0% MA+0.01% TBC 7 11 34 8. 5.0% MA+0.10% TBC 8 8 15 9. 4.7% AN+0.3% VA+0.01% TBC 8 12 35 10. 4.7% AN +03% VA+0.10% TBC-.. 8 10 21 11. Control (no inhibitor) 18 1 31 1 55 B.VAGUUM DISTILLED UNDER NITROGEN Color Values Example 4 Days 14 Days 35 to 45 Days 12. 5.0% AN- 9 11 29 13. 4.7% AN+0.3% MA 9 15 32 14. 4.7% AN+0.3% MA+ TB 9 9 14 15 50% MA+0.1% TBC 8 8 15 16. 4.7% AN+0.3% VA+0.10% TBC- 9 21 17. Control (no inhibitor) 30 C.STEAM DISTILLED (CONTAINS WATER) Example 1 Day 6 Days 18 Days is. 5.0% AN- 11 20 2 19. 10.0% AN. 6 8 20. 4.7% AN+0.3% MA 7 10 21. 9 4% AN+0.6% MA 7 8 22. 5.0% AN-l-0.0l% TBC 10 11 23. 75.0% AN+0.01% TBC 19 20 24. 4.7% AN+0.3% IVLA+0.01% TBC 8 9 25. 9.4% AN+0.6% MA+0.01% TBC..- 8 10 26. 10.0% AN+0.01% MEHQ 19 70 27. 25.0% AN+0.01% MEHQ 5 6 28. Control (no inhibitor) 23 70 1 Indicates positive test; for polymer. 2 14 days.

Example 29 The folowing example illustrates the production of fibers produced from acrylonitrile, methyl acrylate, and Z-methyl-S-vinyl pyridine where the latter compound has been treated with a stabilizing composition of this invention.

A polymer is prepared by copolymerizing a mixture of 89.6 parts by weight acrylonitrile, 5.7 parts by weight methyl acrylate, 4.7 parts by weight 2-methyl-5-vinyl pyridine, and 0.05 part by weight 1,2dihydroxy-4-tertiary-butyl benzene according to the procedure of U.S. Patent No. 3,065,211 using hydrogen peroxide as a catalyst and l-thio-glycerol as an activator. The Z-methyl-S- vinyl pyridine is stabilized for storage before use with 5% of the 89.6/5.7 parts by Weight blend of acrylonitrile and methyl acrylate and the 0.05 part by weight of 1,Z-hydroxy-4-tertiary-butyl benzene noted above as the starting materials for the copolymer. The resulting polymer and fibers spun therefrom are of satisfactory color and do not develop color'upon aging.

From Table II it will be noted that the color stabilizing effect is usually related directly to the concentration of inhibitor. However, with TBC the higher concentrations produce an increase in color. This is probably because the inhibitors themselves become discolored. The steam distilled MVP contains some water and is more difficult to stabilize.

AN gives increasingly better color with increasing concentrations. This is true also with the blend of AN and MA. The blend ratio of 94/6 AN/MA is not critical and higher ratios of MA can be usedso long as it does not give a final polymer of undesirable properties. AN is found to be a suificient inhibitor for storage up to 14 days when used alone, but is better when used with methyl acrylate (MA) or vinyl acetate (VA), and better still when about 0.01% to about 0.1% TBC by weight of MVP is added along with MA or VA.

The preferred range of concentration of the blend of AN and alkyl acrylate is between about 5 and about 10% based on the weight of the MVP. Higher concentrations are satisfactory except for the hazard resulting from the higher vapor pressure in the inhibited MVP which presents an appreciable fire and explosion potential. This hazard puts a practical limit of about 10% on the concentration of the acrylonitrile-acrylate blend. As little as 1%. is satisfactory for short periods of storage.

Acrylates or methacrylates suitable for purposes of this invention can be represented by the formula wherein R is hydrogen or methyl, and R is an alkyl group. The preferred embodiment comprises those compounds wherein R is lower alkyl, i.e., those containing up to four carbon atoms. More preferred yet are those compounds wherein R is methyl, i.e., methyl acrylate and methyl methacrylate, since they are quite satisfactory, not only as stabilizing agents, but also as copolymer constituents. Other alkyl acrylates are satisfactory stabilizers for MVP but should not be used in excess of 0.5% based on the weight of the MVP. Since the ultimate use of the copolymer is in spinning fibers, large amounts of longer chain or modified alkyl acrylates or alkacrylates may give unsatisfactory properties to the final polymer and fibers spun from it.

When acrylonitrile, alkyl acrylate, and a small amount of TBC are used for stabilizing MVP it is not necessary to remove any of the inhibitors before preparing polymers such as that shown above since the inhibitory effect is neutralized by the polymerization catalyst and activator.

It has been found that the most color-stable fibers are produced from MVP which is capable of being stored for at least 35 days without developing a color rating greater than 21. When the MVP possesses greater color than this, it'will begin to be noticeable in spun fibers. The following combinations of stabilizers from Table II are preferred for use in MVP for the production of white, acid dyeable fibers:

AN+MA+TBC AN+VA+TBC AN+T BC MA+TBC The preferred composition is: 4.7% AN, 0.3% MA and 0.10% TBC. Larger quantities of AN and MA can be used if desired but larger quantities of TBC will tend to increase the color of the copolymer. Hydroquinone or the methyl ether of hydroquinone can be used instead of TBC but they are less satisfactory. For short periods of time AN or MA alone will stabilize MVP adequately but for longer periods, beyond 14 days, it is necessary to include TBC.

As many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as de fined in the appended claims.

What is claimed is:

1. A new composition of matter comprising an alkyl vinyl pyridine and a stabilizing amount of (A) a poly-' hydroxy aromatic compound, and (B) at least one member selected from the class consisting essentially of acrylonitrile and compounds of the formula wherein R is a radical selected from the class consisting of hydrogen and methyl, and R is a lower alkyl group. 2. The composition of claim 1 wherein said alkyl vinyl pyridine is 2-methyl-5-vinyl pyridine.

3. The composition of claim -1 wherein (A) is 1,2-dihydroxy-4-tertiary-butyl benzene.

4. The composition of claim 1 wherein (B) is at least one member selected from the class consisting essentially of acrylonitrile, methyl acrylate, and methyl methacrylate.

5. A new composition of matter comprising Z-methyl- 5-vinyl pyridine and a stabilizing amount of (A) 1,2-dihydroxy-4-tertiary-butyl benzene, and (B) at least one member selected from the class consisting of acrylonitrile, methyl acrylate, and methyl methacrylate.

6. A new composition of matter comprising an alkyl wherein R is a radical selected from the class consisting vinyl pyridine and a stabilizing amount of (A) 1,2-diof hydrogen and methyl, and R is a lower alkyl group. hydroXy-4-tertiary-butyl benzene, (B) at least one member selected from the class consisting of acrylonitrile, References Cited by the Examiner methyl acrylate, and methyl methacrylate, and (C) vinyl 5 acetate. UNITED STATES PATENTS 7. A method for stabilizing alky-l vinyl pyridines which 3,043,672 7/1962 Ecke et a1. 26045.95 comprises addlng to said alkyl vinyl pyndmes a Stablllllllg 3,065,211 11/1962 Milford et a1. 260G855 amount of (A) a polyhydroxy aromatic compound, and

(B) at least one member selected from the class consist- 10 ing of acrylonitrile and compounds of the formula WALTER C Primary Exammer- ALAN L. ROTMAN, Assistant Examiner. 

1. A NEW COMPOSITION OF MATTER COMPRISING AN ALKYL VINYL PYRIDINE AND A STABILIZING AMOUNT OF (A) A POLYHYDROXY AROMATIC COMPOUND, AND (B) AT LEAST ONE MEMBER SELECTED FROM THE CLASS CONSISTING ESSENTIALLY OF ACRYLONITRILE AND COMPOUNDS OF THE FORMULA 